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Spiral classifier and hydrocyclone are both mineral processing classifiers. The mineral processing classifier generally include four kinds, increased flow hydrocyclone classifier, cone classifier, a centrifugal classifier( hydrocyclone ) and mechanical classifier ( rake classifier, spiral Classifier, and Floating tank classifier). Today, we will only choose Spiral classifier and hydrocyclone this two equipment to make a detailed comparison, that is because they are the most widely used classifiers in our mill plant, at present.
Spiral Classifier is a kind of mechanical classifier, and it is composited by a u-shaped water tank, spiral device, transmission device, lifting mechanism, bearings and other parts.
The working principle of spiral classifier is: the milled pump was fed into the u-shaped slot from spiral classifier’s feeding mouth, after the continuous rotations and stirrings of the spiral device, the light, and fine particles were suspended in the pulp surface and flowed from the overflow dam; and the thick and heavy particles were settled to the bottom, transported by the spiral device to the port of discharge, re-entered the mill grinding.
There are generally two spiral classifier classification methods, one is in accordance with the number of the screw shaft, it can be divided into single and double spiral classifier spiral classifier; Another kind is according to the overflow dam height, it can be divided into high low and submerged.
Hydrocyclone is a kind of using centrifugal force role grading equipment, mainly made up by the feed tube, cone, cylinder shell, sand mouth and overflow pipe, etc.
The working principle of hydrocyclone is: under the pressure of 0.5-2.5 kg / cm2 in the inlet, the pulp was feed into the cyclone cylinder along the along the tangent direction of the feed tube. A great deal of centrifugal force was produced because of the rotations of the inside part of hydrocyclone, under the action of centrifugal force, the coarser one was thrown to the wall, along with the spiral descent flow, and was discharged from the discharge mouth.
Advantages of hydrocyclone are: It is simply constructed and has no moving parts; the small size covered small footprint; it has large capacity per unit area, and it’s very convenient to operate and maintain, so, the cost is very low; what’s more, the classification efficiency and sorting accuracy are higher; and it needs lesser quantity and time for pulp to stay; the advantages are more apparent when working together with a large ball mill. Of course, the hydrocyclone has its shortcomings, such as the pulp needs the head of the pump to delivery; it needs stable working pressure when working, and it has a higher demand to the particle size and concentration of the pulp, what else is that it can be worn more serious.
Spiral classifier has more significantly highlighting advantages compared with hydrocyclone, such as, It is reliable and easy to operate; the staging area is smooth and finer overflowed particle size can be obtained. What’s more, the trough slope is easier for sand returning into to the ball mill. In addition to these, some of domestic mining machine manufacturers make some improvements to a spiral classifier, for example，Yantai Xinhai mining machinery company has added a sand-returning automatic lifting device in the sand-returning end of the spiral classifier, in order to substitute the tablespoons head of the ball mill. That makes the ball mill run more smoothly.
Shortcomings of spiral classifier are: It’s relatively cumbersome and the classification efficiency is low; the spindle is frangible and the maintenance is extremely inconvenient; and it has poor overflow bearing seal at the bottom of spiral classifier; what else, a finer classification overflow fineness is difficult to get especially when the asked overflow granularity is -0.074mm and accounts more than 90%.
Overall, spiral classifier and hydrocyclone are widely applied in our country, each of them has his strong point.